1. Field of the Invention
The present invention is in the field of apparatus and method used first to internally clean a transmission (i.e., by adding and circulating a cleaning fluid to the used ATF), and then to discharge old ATF from the automatic transmission. While the old ATF is discharged, new ATF is simultaneously delivered into the transmission. Thus, the apparatus and method may be used to clean an automatic transmission and exchange the old fluid with new, all while the transmission is installed in a vehicle, such as in an automobile, truck or bus, for example. Particularly, the present apparatus and method addresses the problem of servicing those automotive vehicles having automatic transmissions with internal transmission pumps of low-flow or low-pressure characteristics. These low-pressure and low-flow characteristics make this type of transmission particularly difficult to clean and service.
2. Related Technology
Many conventional machines and methodologies presently exist for withdrawing used ATF from an automotive automatic transmission, and for replacing this old fluid with new fluid, either sequentially or simultaneously while the old fluid is removed or discharged from the transmission.
The traditional method of changing the fluid in an automatic transmission (i.e., by dropping the transmission pan and replacing the fluid and transmission filter) has fallen into disfavor because it leaves such a large percentage of the old fluid in the transmission.
More favored at the present time are machines and methods which employ the internal pump of the transmission to discharge the ATF, while new ATF is supplied into the transmission on a volume matching basis. The vehicle engine is ordinarily operated in order to drive the internal pump of the transmission. This operation of the vehicle engine is usually accomplished by running the vehicle engine with the transmission in "neutral" or "park", with most of the old ATF being exchanged in this way (i.e., without the drive wheels spinning or the transmission clutches being cycled). In this way, the old ATF is flushed from the transmission, torque converter, ATF cooler, and connecting conduits of the transmission system. Alternatively, the vehicle can be operated on a chassis roller stand, allowing the drive wheels to spin and the clutches of the transmission to be cycled. Operation of the vehicle engine powers the internal fluid pump of the transmission and facilitates flow of ATF through the torque converter and other parts of the transmission system, effectively flushing out the old ATF and replacing it with new fluid. In this latter case, the transmission clutches will also be cycled to remove old ATF.
A cleaning machine for an automotive automatic transmission is known according to U.S. Pat. No. 5,337,708, issued Aug. 16, 1994 to We-Yu Chen. The '708 patent is believed to teach a transmission fluid change machine in which an external ATF circulation loop of the transmission is opened, with part of the machine completing this loop in one mode of operation. The used transmission fluid, possibly with a transmission flushing solution, is circulated in the external circulation loop as completed by the machine. When operated in an exchange/refill mode, the machine receives old transmission fluid and supplies new fluid at a selected pressure or volume delivery rate.
The machine taught by Chen is intended to be operated from the 12 volt power supply of the automobile or other automotive vehicle being serviced. The new transmission fluid tank of this device appears to be provided with a level sensor, so that the system can be reverted to loop configuration (filtration/flushing) should the level of new ATF drop too low. An external power-driven pump is utilized to move new ATF from the fluid tank to the transmission being serviced. However, it is not clear from this patent that in the event the power supply to this device is interrupted or the pump ceases to operate, that the configuration of the device is reverted to loop form so that the transmission of the vehicle being serviced is not damaged by being operated with insufficient ATF. Although this patent asserts that a power failure will cause reversion of the apparatus to loop configuration in the event of a power failure, how this change in configuration is to be effected or powered does not appear to be explained.
Another transmission fluid change apparatus is disclosed by U.S. Pat. No. 5,318,080, issued Jun. 7, 1994 to James P. Viken. The '080 patent is believed to disclose an apparatus in which supply of the new ATF is provided by a pressurized storage container, which container is pressurized by the inflow of used ATF pumped from the transmission by its own internal pump. The storage container has a chamber which is separated by a flexible wall (i.e., a rolling-diaphragm piston) into two sub-chambers expanding and contracting in opposition. As used ATF from the transmission is received into one sub-chamber, new ATF is displaced from the other sub-chamber to the transmission. Another embodiment of this device uses two separate containers, one receiving the old ATF and the other holding new ATF. Air displaced from the one container is routed into the other with the idea that the air will drive the new ATF into the transmission. A pressurized air assist to this delivery of new fluid is provided. There is considerable uncertainty with these machines that the rate of new fluid delivery really matches the rate of old fluid draining from the transmission under service.
Another transmission service machine is known according to U.S. Pat. No. 5,370,160, issued Dec. 6, 1994 to Zachary T. Parker. The '160 patent is believed to disclose a service machine in which the external ATF fluid return loop for the transmission is completed by a reservoir from which the fluid is drawn by a pump. Accordingly, in the event that operation of the pump is interrupted while the serviced vehicle continues to operate, the transmission of the vehicle is at risk of damage from dry running. A separate pump is used to supply new ATF to the transmission, but this pump may suffer from the same power supply interruption, so that the transmission is still at risk of damage from dry running. The Parker '160 patent does not appear to provide a closed external ATF circulation loop for the transmission being serviced (other than the one relying on operation of an external power-driven pump), and does not use a three-way valve to complete or open such an external ATF circulation loop.
Still another apparatus for exchanging the fluid of an automatic transmission is known in accord with U.S. Pat. No. 5,447,184, issued Sep. 5, 1995 to Eduardo Betancourt. The '184 patent is believed to disclose an apparatus in which a reservoir for new ATF is provided so that the volume of new fluid supplied to the transmission can exceed the withdrawn volume. The '184 patent appears to include a sensor operating a bell to bring the attendant's attention to the fact that the supply of new ATF is at risk of running out. However, if the attendant is either not close at hand to hear the bell or is inattentive, the transmission may still be damaged if the supply of new ATF runs out while the transmission is being flushed. Still further, the device taught by the '184 patent is not believed to provide any safeguard to protect the automatic transmission in the event of a power failure to the apparatus while the transmission is being flushed during operation.
Finally, an apparatus for flushing an automatic transmission is known according to U.S. Pat. No. 5,472,064, issued Dec. 5, 1995. The feature which the '064 patent appears to contribute to the art is the use of a conventional directional flow control valve. This flow control valve is inserted into the fluid flow conduits connecting the service machine to the external loop of the transmission, and allows connection of the apparatus to the external ATF circulation loop (i.e., the ATF cooler loop) of the transmission with no need to take note of the direction of fluid circulation in this loop. If the internal fluid flow direction of the machine happens to be correct as connected, there is no need to change the valve position. In the event the internal fluid flow direction of the machine is opposite to that of the transmission connection, then reversing the position of the flow control direction valve will match the internal flow direction to the direction of the fluid flow in the external ATF flow loop of the transmission. This machine requires attention and manual intervention of the technician to correct the fluid flow directions so that service can begin in the event that by chance these connections to the transmission are not right to begin with.
None of these conventional transmission service machines address or solve the problem presented by some low-flow or low-pressure automatic transmissions. That is, some transmissions have an internal pump which does not provide the required pressure or fluid flow volume necessary to effect exchange of the transmission fluid (ATF) using conventional machines and methods for this purpose.